Optical (i.e., transport) networks and the like (e.g., DWDM, Synchronous Optical Network (SONET), Synchronous Digital Hierarchy (SDH), Optical Transport Network (OTN), Ethernet, and the like) at various layers are deploying control plane systems and methods. Control planes provide automatic allocation of network resources in an end-to-end manner. Exemplary control planes may include Automatically Switched Optical Network (ASON) as defined in ITU-T G.8080/Y.1304, Architecture for the automatically switched optical network (ASON) (02/2005), the contents of which are herein incorporated by reference; Generalized Multi-Protocol Label Switching (GMPLS) Architecture as defined in IETF Request for Comments (RFC): 3945 (10/2004) and the like, the contents of which are herein incorporated by reference; Optical Signaling and Routing Protocol (OSRP) from Ciena Corporation which is an optical signaling and routing protocol similar to PNNI (Private Network-to-Network Interface) and MPLS; or any other type control plane for controlling network elements at multiple layers, and establishing connections therebetween. Control planes are configured to establish end-to-end signaled connections such as Subnetwork Connections (SNCs) in ASON or OSRP and Label Switched Paths (LSPs) in GMPLS and MPLS. Control planes use the available paths to route the SNCs/LSPs and program the underlying hardware accordingly.
For Layer 0 Networks (DWDM), it would be advantageous to calculate routes which adhere to the network constraints/nodal characteristics or the inventory supported on the nodes in the path through the control plane. This could include regenerator configuration, partial connectivity, wavelength (X) contention, wavelengths supported, etc. In Layer 0 networks some node level parameters are not flooded to the network through the control plane. This is because the constraints could be many and it is inefficient to flood them into the network. This is not true for Layer 1 networks since the constraints are limited, they are all flooded in the network. Examples of some hidden constraints in Layer 0 networks are intra nodal connectivity and regenerator related information/constraints. Of course, these constraints in Layer 0 network can invalidate a route during call setup.
There are a couple conventional options to solve these limitations, namely 1) flood all the hidden information/constraints at Layer 0 and incorporate these into the path computation engine/validation, 2) use crank backs to re-route the call if faced with problems based on the constraints, or 3) rely on a centralized approach. Again, it would be non-optimal to advertise all this information and use it in path computation. This impacts scalability of the network for control plane applications. Relying on crank backs can lead to blocking/delayed setup of services. Thus it is non-optimal and inefficient. Finally, the centralized approach is static and can be based on outdated configurations which can also lead to crank backs.
In conventional Layer 0 control plane networks, when a crank back happens in the network not much information is present in a Release message about the exact cause of the crank back which will help in making alternative decisions effectively at the originating node. Also, the crank back originates at the first instance of failure along the setup path. There could be multiple crank back possibilities along the path across multiple nodes and links that are beyond the first point of call rejection and are not visible in the existing model. The above scenario is quite possible when the alternate paths to the destination are not fully diverse. This could result in more retries along the problem path and crank back failures due to lack more insight further along the path from the point of crank back.